Aerospace Engineering Commons^™

Desensitizing Flame Structure And Exhaust Emissions To Flow Parameters In An Ultra-Compact Combuster, Adam K. Parks

Theses and Dissertations

A major thrust of turbine engine research is to improve both efficiency and thrust-to-weight ratio of the engine. A promising solution to this challenge is the Ultra-Compact Combustor (UCC). The UCC shortens the axial length of the combustor by performing combustion circumferentially on the outer diameter of the engine. The reduction in axial length yields significant weight savings and increases the thrust-to-weight ratio. The design also increases combustion efficiency by performing the combustion in a centrifugally loaded environment which allows unreacted particles to remain in the combustor sufficiently long enough to become combustion products. The Air Force Institute of Technology …

Application Of Multi-Input Multi-Output Feedback Control For F-16 Ventral Fin Buffet Alleviation Using Piezoelectric Actuators, Tomoyuki D. Ono

Theses and Dissertations

Control of structural vibrations has been a popular topic. Use of MFC piezoelectric actuators and co-located sensors allows for an active rather than passive control method. The F-16 ventral fin is susceptible to buffet induced vibrations and is a perfect test structure for active vibration control for flight-testing. The research follows the previous ACTIVE FIN project and improves on the design by increasing the number of actuator layers, available actuator power, and using multi-input multi-output (MIMO) control algorithms. The research involved experimental identification of the ventral fin and its principle strain directions, selection of system components, determination of mathematical plant …

Development And Testing Of A Rotating Detonation Engine Run On Hydrogen And Air, Jason C. Shank

Theses and Dissertations

Rotating detonation engines (RDEs) have the potential for greater efficiencies over conventional engines by utilizing pressure gain combustion. A new modular RDE (6 in diameter) was developed and successfully run on hydrogen and standard air. The RDE allows for variation of injection scheme and detonation channel widths. Tests provided the operational space of the new RDE as well as characterized detonation unsteadiness. It was found that a smaller equivalence ratio than previous was required to obtain continuous detonations. Also discovered was VCJ was reached in the RDE, but not sustained.

Creep Of Hi-Nicalon S Ceramic Fiber Tows At Elevated Temperature In Air And In Steam, Benjamin R. Steffens

Theses and Dissertations

Structural aerospace components require materials to have superior long-term mechanical properties that can withstand severe environmental conditions, such as high temperatures, high pressures and moisture, whilst enduring the loads they are designed for. Ceramic-matrix composites (CMCs) are capable of maintaining excellent strength and creep resistance at high temperatures, which make them attractive candidate materials for aerospace applications, particularly in propulsion. Silicon Carbide (SiC) ceramic fibers have been used as constituent materials in CMCs, although oxidation of the SiC to SiO₂ has been a known degredation mechanism. Recently developed near stoichiometric SiC fibers have shown significant improvements in thermochemical stability; …

A Finite Element Analysis Of A Carbon Fiber Composite Micro Air Vehicle Wing, Theodore A. Szelag

Theses and Dissertations

Micro-air vehicles (MAV)s provide a valuable and low observable way to do the jobs that the Air Force deems to be dull, dirty and dangerous. Basing the design of an MAV wing on that of a biological counterpart will provide a proven design that is capable of achieving the mission requirements. This research is designed to analyze the design and manufacturing of a wing based off the Manduca Sexta.

Inaccuracies in the fiber orientation can result in substantial changes in the material properties. Experimental vibration data of composite material samples manufactured using a three-ply [0/90/0] small non-homogenous fiber composite provided …

Build Up And Operation Of An Axial Turbine Driven By A Rotary Detonation Engine, Jonathan R. Tellefsen

Theses and Dissertations

Detonation combustors provide advantages over current deflagration combustors due to their pressure gain and simplicity of design. Rotary detonation engines (RDEs) offer advantages over pulsed detonation engines (PDEs) due to a steadier exhaust and fewer total system losses. All previous research on turbine integration with detonation combustors has focused on utilizing PDEs to drive axial and centrifugal turbines. The objective of this thesis was the integration and testing of an axial turbine driven by a rotary detonation engine (RDE) to determine turbine operability. In pursuit of this objective, convergent nozzle sections were placed on the RDE to simulate the back-pressurization …

Empirical Characterization Of Unconstrained Tape Spring Deployment Dynamics, Daniel M. Williams

Theses and Dissertations

Satellite cost and mission capability are very sensitive to mass requirements. Mass or volume savings in one component will either lower total spacecraft mass, or provide greater margin for design error in other components. Solar arrays and antennas in particular are often driven by launch vehicle volume constraints instead of mission needs. Deployable structures provide more on-orbit area for both solar arrays and antennas, while occupying less space during launch. These structures therefore, help address these constraints and have been proven as efficient solutions for many years. Tape springs are one example in this category of structures which offer greater …

Boundary Layer Measurements In The Trisonic Gas-Dynamics Facility Using Particle Image Velocimetry With Co₂ Seeding, Daniel B. Wolfe

Theses and Dissertations

Particle image velocimetry (PIV) is utilized with solid carbon dioxide (CO₂) seeding material to conduct boundary layer measurements in the test section of the Air Force Research Laboratory's Trisonic Gas-dynamics Facility (TGF), which has a 24 inch by 24 inch cross-section. Freestream velocity was set at Mach 0.3, Mach 0.5, or Mach 0.8 while stagnation pressure ranged from 500 to 2400 pounds per square foot (psf). High pressure liquid CO₂ was directed through expansion nozzles into shroud tubes which led to solidified particles in the wind tunnel stagnation chamber. Two different sets of shroud tubes were used …

Trajectory Control And Optimization For Responsive Spacecraft, Costantinos Zagaris

Theses and Dissertations

The concept of responsive space has been gaining interest, and growing to include systems that can be re-tasked to complete multiple missions within their lifetime. The purpose of this study is to develop an algorithm that produces a maneuver trajectory that will cause a spacecraft to arrive at a particular location within its orbit earlier than expected. The time difference, delta t, is used as a metric to quantify the effects of the maneuver. Two separate algorithms are developed. The first algorithm is an optimal control method and is developed through Optimal Control Theory. The second algorithm is a feedback …

Reynolds Number Effects On Thrust Coefficients And Piv For Flapping Wing Micro Air Vehicles, John P. Tekell

Theses and Dissertations

For the last several years the Air Force Institute of Technology (AFIT) has conducted research in aerodynamics for flapping wing micro air vehicles (MAVs). The focus of this research was to augment this effort by measuring thrust, velocity, and torque in tanks of water and glycerin using a scale and a reaction torque cell. The results for different flapping mechanisms are compared to a rotating propeller with the goal of elucidating the design trade space between rotorcraft and flapping wings at Reynolds numbers less than 100,000. In addition, flow visualization and quantitative velocity data were captured in the wake of …

Integration Of Cold Atom Interferometry Ins With Other Sensors, Aaron J. Canciani

Theses and Dissertations

Inertial navigation systems (INS) using cold-atom interferometry are currently under development, and sensors in these systems are expected to be several orders of magnitude more ccurate than current navigation grade sensors. This signi cant increase in accuracy motivates the need to explore how these high accuracy inertial navigation systems can be integrated with other sensors. This research focuses on methods of integrating cold atom interferometry INS with conventional navigation grade INS, as well as with GPS. Results from a full 6 degree of freedom simulation show that integrating CAI INS with navigation grade INS is a successful way to address …

Modeling, Simulation, And Flight Test For Automatic Flight Control Of The Condor Hybrid-Electric Remote Piloted Aircraft, Christopher Giacomo

Theses and Dissertations

This thesis describes the modeling and verification process for the stability and control analysis of the Condor hybrid-electric Remote-Piloted Aircraft (HE-RPA). Due to the high-aspect ratio, sailplane-like geometry of the aircraft, both longitudinal and lateral/directional aerodynamic moments and effects are investigated. The aircraft is modeled using both digital DATCOM as well as the JET5 Excel-based design tool. Static model data is used to create a detailed assessment of predictive flight characteristics and PID autopilot gains that are verified with autonomous flight test. PID gain values were determined using a six degree of freedom linear simulation with the Matlab/SIMULINK software. Flight …

Aircraft Course Optimization Tool Using Gpops Matlab Code, Ryan D. Gauntt

Theses and Dissertations

Aircraft course planning between two points in a clear, no threat environment is easy and straightforward. However, the addition of various threats can greatly increase the difficulty and complexity of course planning. Placing new waypoints along the edge of each threat, mostly skirting the dangerous environment, may not prove too difficult, but such courses are far from optimal. Given aircraft, environment, and time constraints it is likely a much more optimal path exists between any given start and end points. This research focuses on determining the feasibility of using the General Pseudospectral Optimization Software program files written for the MATLAB …

Plume Characterization Of Busek 600w Hall Thruster, Duc Minh Bui

Theses and Dissertations

The BHT-600W thruster has a high potential to place on various commercial and military satellites as a main propulsion system for orbit maintenance and orbit maneuvering. Therefore, the thruster's performance characteristics and parameters were evaluated for various operating conditions. These parameters include thrust, power consumption, mass flow rate, and efficiencies. Various plume properties were measured and characterized for the thruster to include exhaust beam profile and ion species distribution. The faraday probe was used to examine the thruster plume current density while the ion species fractions were determined by the ExB probe. The inverted pendulum thrust stand was also utilized …

Space Science Research And Stem Activities At Morehead State University, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Professor Bob Twiggs titled "Space Science Research and STEM Activities at Morehead State University" from March 7, 2012.

Arliss: A Rocket Launch For International Student Satellites - Launch Report For 2011, David Raimondi

Robert "Bob" Twiggs STEM Education Collection

A report written by David Raimondi titled "ARLISS A Rocket Launch for International Student Satellites Launch Report for 2011" from March 7, 2012.

An Adjoint Method To Determine The Effective Material Properties Of An Ablator, Emma Johnstone

Ablation Workshop

The determination of the effective thermal properties of a material from thermocouple data has always been very labour intensive. Similarly determining the Arrhenius parameters for a decomposition model from thermo-gravimetric analysis is also very time-consuming. There is little formalisation of the procedures used to determine the material properties. Despite the fact that some effort has been devoted to this topic in the literature, it is not clear whether comparable effective material properties data would result if several groups used the same experimental data. The FGE Ablation code FABL has been written in an adjoint form and has successfully been used …

Ultrasonic Thermometry For Recession Measurements In Ablative Materials, Joseph A. Lloyd, Donald E. Yuhas

Ablation Workshop

Recent developments in ultrasonic instrumentation & sensors, improved signal processing, and high speed data acquisition have rekindled interest in ultrasonic thermometry and made temperature localization feasible and economically attractive to a wider range of applications. Ultrasound-based temperature measurements offer several advantages: they are non-intrusive, have high temporal response, isolate the sensor from explosive or chemically harsh environments and do not adversely influence thermal transport. Ultrasonic thermometry techniques rely on precise measurements of ultrasonic time-of-flight (ToF) which forms the basis for many applications including measurements of flow, heat flux, temperature, ablation and strain. In this report, we characterize the ultrasonic propagation …

A Statistics-Based Material Property Analysis To Support Ablation Simulation Uq Efforts, Sean R. Copeland, Juan Alonso, Milad Mahzari, Ioana Cozmuta

Ablation Workshop

Accurate characterization of entry capsule heat shield material properties is a critical component in modeling and simulating Thermal Protection System (TPS) response in a prescribed aerothermal environment. The thermal decomposition of the TPS material during the pyrolysis and charring processes is typically poorly characterized and results in large uncertainties in material properties as inputs for ablation models. These material property uncertainties contribute to large design margins on flight systems and cloud re-construction efforts for data collected during flight and ground testing, making revision to existing models for entry systems more challenging. This work focuses on the following areas of interest …

Efficient Uncertainty Quantification & Sensitivity Analysis For Hypersonic Flow And Material Response Simulations Under Inherent And Model-Form Uncertainties, Serhat Hosder

Ablation Workshop

Accurate numerical prediction of coupled hypersonic flow fields and ablative TPS material response is challenging due to the complex nature of the physics. The uncertainties associated with various physical models used in high-enthalpy hypersonic flow and material response simulations can have significant effects on the accuracy of the results including the heat-flux and temperature distributions in various layers of ablating TPS material. These uncertainties can arise from the lack of knowledge in physical modeling (model-form or epistemic uncertainty) or inherent variations in the model inputs (aleatory or probabilistic uncertainty). It is important to include both types of uncertainty in the …